1. Field of the Invention
The present invention generally relates to a liquid-cooling type cooling device which uses circulating liquid and an image forming apparatus using the liquid-cooling type cooling device which prevents temperature inside the image forming apparatus from being increased.
2. Description of the Related Art
Recently, as image forming apparatuses such as a printer, a facsimile machine, and a multifunctional apparatus including a printing function and a facsimile transmitting function, an image forming apparatus using an electrophotographic system or an inkjet system has been well known. Many units and members whose temperature is increased corresponding to operations of the apparatus are disposed in the image forming apparatus using the electrophotographic system or the inkjet system. As the units and the members whose temperature is increased in an image forming apparatus using the electrophotographic system, for example, there are, a reading unit which reads a document by radiating light on the document, a photoconductor body on which an electrostatic latent image is formed by a writing unit, a developing device which forms a visual image by supplying toners onto the electrostatic latent image on the photoconductor body while stirring the toners, the toners which are subjected to friction by the stirring, and a fixing device which fixes the visual image transferred onto a recording medium (paper) by using heat and pressure.
When the temperature rises, some functions do not operate well in the image forming apparatus. Therefore, generally, in order to cool a temperature risen unit or member, a cooling fan is used by air cooling. Hereinafter, in some cases, the units and the members are referred to as temperature rising parts. However, recently, in the image forming apparatus, a heating value has been increased due to high-speed printing, and a heating generation density has been increased due to a small-sized apparatus. Consequently, it has been difficult for the image forming apparatus to sufficiently cool the temperature rising parts by the air cooling.
In order to solve the above problem, cooling devices have been proposed in which cooling efficiency is higher than that of the cooling device by the air cooling. As one of the proposed cooling devices, there is a liquid-cooling type cooling device. In the liquid-cooling type cooling device, a liquid cooling medium is circulated, heat at a temperature rising part is absorbed by the liquid cooling medium at a heat receiving section, and the heat of the liquid cooling medium is radiated at a radiator. In the liquid-cooling type cooling device, the cooling performance is high, and the heat can be absorbed at the heat receiving section in high efficiency. Therefore, the liquid-cooling type cooling device has been proposed to be installed in an image forming apparatus (for example, see Patent Document 1).
However, since water is evaporated from paper inside the image forming apparatus, humidity becomes higher inside the image forming apparatus than that outside the apparatus. In particular, the humidity is likely to become higher in the image forming apparatus using the liquid-cooling type cooling device than an image forming apparatus using an air-cooling type cooling device which ventilates. In the image forming apparatus using the liquid-cooling type cooling device, temperature on outer surfaces of the heat receiving section having high heat receiving efficiency becomes lower than ambient temperature inside the image forming apparatus, and the temperature on the outer surfaces of the heat receiving section becomes a dew point or less. Consequently, there is a risk that dew is condensed on the outer surfaces of the heat receiving section. When the size of a water droplet formed by the dew condensation becomes large and the water droplet drops from the heat receiving section, a part surrounding the heat receiving section is wetted. When the water droplet drops on image forming units or members such as the photoconductor body, the developing device, and the paper; the image quality is degraded due to blurring of the image or the paper may be stained.
In order to prevent the size of the water droplet from being increased when the dew is condensed, a hydrophilic material is applied onto the outer surfaces of the heat receiving section (for example, see Patent Document 2).
[Patent Document 1] Japanese Unexamined Patent Publication No. 2005-164927
[Patent Document 2] Japanese Unexamined Patent Publication No. 2007-293111
In Patent Document 2, the size of the water droplet is prevented from being increased when the dew is condensed; however, the water droplet is not surely prevented from being dropped from the heat receiving section of the liquid-cooling type cooling device.